COMPETITIVE AND CO-ADSORPTION BEHAVIORS BETWEEN ADDITIVES FOR Cu ELECTRODEPOSITION INVESTIGATED BY SURFACE-ENHANCE INFRARED ABSORPTION SPECTROSCOPY
Guokun Liu, Shouzhong Zou*, Lee. J. Richter and Thomas P. Moffat
As the dominant technology for fabricating interconnects for microelectronic devices, the science and technology of Cu electrodeposition continues to attracted much attention. The most widely investigated additive system to date is: chloride (Cl-), poly(ethylene glycol) (PEG, mW ~2000 to 6000) and bis-(3-sodiumsulfopropyl disulfide) (SPS), where the accelerating and inhibiting phases derive from synergetic co-adsorption and competitive adsorption between SPS-Cl- and PEG-Cl- respectively.1-2 Although various electrochemical techniques, STM and vibrational spectroscopies1-4 have been used to untangle the co- and competitive adsorption behavior between PEG, Cl- and SPS, little attention has been paid to the role of the interfacial water molecules. Herein, we take advantage of the molecular level vibrational information provided by Surface-Enhanced Infrared Absorption Spectroscopy (SEIRAS) to examine the structure, coverage and dynamics of these additive species with an eye towards understanding their effect on electrochemical reactions at the Cu/ H2SO4 interface. Preliminary in situ results reveal the interactions between i) water and the anions, SO42- and Cl-, ii.) water, anions and PEG, and iii) the competitive dynamics between inhibiting PEG-Cl versus accelerating SPS-Cl species.
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4. L. D’Urzo and B. Bozzini, J. Mater. Sci.: Mater. Electron., 20, 217 (2009).
* on sabbatical leave from the Department of Chemistry,Miami University, Oxford, OH 45056